Ethylene glycol is an important constituent of commercial polyester resins. Also of increasing importance as resin constituents are higher polyols such as 1,4-butanediol. The development of new and improved commercial processes for production of higher polyols is under active investigation.
1,4-Butanediol can be derived from succinic acid, maleic anhydride and other four-carbon organic species, but such methods are not economically attractive. Another method of producing 1,4-butanediol is by the reaction of formaldehyde and acetylene to form 1,4-butynediol as an intermediate, which is subsequently hydrogenated to the desired 1,4-butanediol product.
Other investigators have endeavored to convert acrolein into 1,4-butanediol by subjecting acrolein to hydroformylation conditions, the objective being the formation of succinaldehyde as an intermediate product. The results have been unsatisfactory since the main conversion product recovered from acrolein under hydroformylation conditions is propionaldehyde.
Other efforts to produce 1,4-butanediol have involved hydroformylation of allyl alcohol to yield 4-hydroxybutanal as an intermediate which is subsequently hydrogenated to 1,4-butanediol. The liquid phase hydroformylation of allyl alcohol in the presence of hydroformylation catalysts such as cobalt carbonyl produces significant quantities of propanal, propanol and 2-methyl-3-hydroxypropanal as by-products, in addition to the desired 4-hydroxybutanal.
In U.S. Patent Office Defensive Publication No. 904,021 (Nov. 21, 1972) there is disclosed an improved hydroformylation process for converting unsaturated alcohols into diols. In one embodiment the Publication process involves the hydroformylation of allyl alcohol with rhodium-phosphine complex catalyst to produce a reaction mixture which is subsequently hydrogenated to yield 63 percent 1,4-butanediol and 25 percent 2-methylpropanediol. based on the weight of allyl alcohol charged. For the purposes of economic feasibility, higher conversion yields of 1,4-butanediol from allyl alcohol are desirable for commercial scale operations.
Accordingly, it is a main object of the present invention to provide an improved process for converting acrolein into 1,4-butanediol.
It is another object of the present invention to provide a catalyst for converting acrolein into allyl alcohol in a yield of at least 70 percent.
It is another object of the present invention to provide 4-hydroxybutanal in high yield as an intermediate product in a commercially feasible process for converting acrolein into 1,4-butanediol.
Other objects and advantages shall become apparent from the accompanying description and examples.